What should the humidity be in my house?
The humidity in your house should sit at 40 to 50 percent relative humidity in the rooms you live and sleep in. That is the band where your airways, sleep, eyes, and skin all do best, and it sits safely below the level where mold and dust mites take hold. Federal guidance is looser, below 60 percent, but 40 to 50 percent is the band worth hitting.
What is the right humidity level for a house?
The right humidity level for a house is 40 to 50 percent relative humidity in the rooms you live and sleep in. Relative humidity is how much water vapor is in your air compared with the most it could hold at that temperature. The EPA says keep a home below 60 percent and ideally between 30 and 50 percent. The research consensus tightens that to 40 to 50 percent. Below 30 percent feels dry, and above 60 percent feels heavy. Forty to fifty is the one window where breathing, sleep, eye and skin comfort, and mold prevention all line up at once. A cheap hygrometer or a smart sensor will tell you where your bedroom sits right now, which is the number that matters most.
What does dry air do to your body?
Dry air, meaning indoor humidity below 30 percent, dries out the wet lining your nose and airways use to clean themselves. That mucus lining traps viruses, bacteria, and particles, and tiny hairs sweep them out. When it dries, the sweeping slows, and things that should clear in twenty minutes can sit for hours. In one office study, going from 43 percent down to 15 percent humidity pushed dry-air complaints from about one in ten workers to more than half. Dry air also keeps cold and flu viruses infectious in the air longer, and blunts your body's own defenses against them. It dries the tear film, so eyes sting. It pulls water out of skin, so skin cracks and flares. None of this is dangerous on its own, but it quietly makes you worse at fighting off the things that are.
Can indoor humidity be too high?
Indoor humidity can be too high, and sustained readings above 60 percent flip you to the opposite failure. Mold needs a damp surface for a day or two to take hold, and above 60 percent enough surfaces in a room stay damp long enough to let it. Dust mites, a major indoor allergen, need humidity above roughly 50 percent to thrive and die back below it. This is the trap with running a humidifier too hard, or with a coastal or humid climate where outdoor moisture creeps in overnight. If windows fog up, a room smells musty, or you see growth, dry the room out rather than adding more water.
Is my house more likely too dry or too humid?
Most homes run too dry rather than too humid. If your air conditioner or furnace runs much of the year, your home probably rides at 25 to 40 percent humidity, 10 to 15 points below the target band. Air conditioning pulls water out of the air at the coil as a side effect of cooling. Winter heating warms cold outdoor air that was already dry. Both leave you below where your body wants to be, which is why the bedroom is usually the room to fix first. Humid and coastal homes are the exception and lean the other way.
Where do I start?
- Put a cheap hygrometer or smart sensor in your bedroom and read it over a few days, especially overnight. Guessing is how people overshoot in both directions.
- If you read below 40 percent, raise it before you buy anything: dry laundry on a rack indoors, keep the bathroom door open after a shower, add a few houseplants. Then a cool-mist humidifier in the bedroom closes the rest of the gap.
- If you read above 60 percent, run the bathroom and kitchen exhaust fans, crack a window when weather allows, and only then reach for a dehumidifier.
- Empty and rinse a humidifier daily and clean it weekly. A dirty tank blows mold and bacteria into the room, which defeats the point.
- Fill an ultrasonic humidifier with distilled or demineralized water, not tap, to avoid the fine white mineral dust it otherwise sprays.
What does the science say?
What actually works?
Common questions
Is dry air actually bad for you?
Dry air is not poisonous, but below 30 percent humidity it measurably weakens your airway defenses, keeps cold and flu viruses infectious longer, dries out eyes and skin, and fragments sleep through a stuffy nose. The effect is indirect: it weakens how well you fight off and recover from the things that do cause harm. Holding 40 to 50 percent removes that penalty.
What is the best humidity for sleep?
40 to 50 percent, measured in the bedroom overnight. At that level the lining of your nose stays hydrated, so you avoid the dry-nose congestion and mouth-breathing cycle that fragments sleep. Most bedrooms with the heat or AC running sit below that band, which is why a bedroom humidifier is the usual first fix.
What should room humidity be?
40 to 50 percent in the rooms you actually use, the ones where you sleep and spend the day. Humidity varies room to room inside a home, so the bedroom reading overnight matters more than a whole-house average. Most homes running heat or air conditioning sit below that band, closer to 25 to 40 percent, so the usual fix is adding a little moisture back, not pulling it out.
Is 60 percent humidity too high in a house?
Sixty percent is the top of the safe range in a house, not an emergency, but it is not where you want to stay. EPA guidance is to keep a home below 60 percent, and sustained readings above it invite mold and feed dust mites, which thrive above roughly 50 percent. A short spike after a shower is fine, but weeks parked there is the problem. Fogged windows or a musty smell mean you are too wet, so dry the room with ventilation or a dehumidifier rather than adding moisture.
Does a humidifier really help, or is it just comfort?
A humidifier does more than make a dry home comfortable. A bedroom held at 40 to 50 percent overnight keeps your airway defenses working, reduces how long airborne viruses stay infectious, and eases dry eyes and skin. In a preschool study, humidified classrooms had a little over two times fewer flu-like illnesses than unhumidified ones. The catch is hygiene. Clean it, or it becomes a mold source itself.
How do I measure the humidity in my house?
A standalone hygrometer or a smart air-quality sensor reads the humidity in your house directly, usually within a couple of percent. Put one in the bedroom and one in the main living area, and watch them across a few days and overnight. The number swings with the AC, the furnace, showers, and outdoor weather, so a single spot reading tells you little.
Is 50% humidity in a room too high?
No. Fifty percent is the top of the ideal band, not above it, so a room reading 50 is where you want to be. Below 30 percent is too dry. 30 to 40 percent is dry. 40 to 50 percent is the target. 50 to 60 percent is fine for you but close enough to dust mite conditions that you do not want a room parked there for weeks. Sustained above 60 percent is where to act. EPA guidance is to keep a home below 60 percent and ideally between 30 and 50 percent. One caveat the room number cannot give you: mold starts on a damp surface rather than in the air, so a cold exterior wall or window frame can be wet enough to grow mold while the room itself reads a comfortable 55. A brief spike after a shower does not count, since what matters is where the room sits across days.
Is 72 indoor humidity high?
Yes, and it is high enough to act on rather than watch. Anything sustained above 60 percent is where mold and dust mites get the conditions they need, so 72 is well past the line, and EPA guidance is to keep a home under 60. Run the air conditioning or a dehumidifier, use the bathroom and kitchen exhaust fans every time, and look for the source, because a reading that high usually means water is coming from somewhere: a crawlspace, an unvented dryer, a slow leak, or humid outdoor air let in on the wrong day. The number to watch after that is not the room average but the cold surfaces, since those stay damp long after the room reads normal.
Is 30 indoor humidity too low?
Yes, for a room you sleep or spend the day in. EPA's home guidance runs 30 to 50 percent, so 30 sits inside the official range and at the worst end of it, a full ten points under the 40 to 50 percent band your airways, sleep, eyes, and skin all do best in. Below 30 percent the wet lining that sweeps viruses and particles out of your nose and airways thickens and slows, exhaled viruses stay infectious in the air longer, and dry eye and dry skin symptoms climb. Raise it before you buy anything: dry laundry on a rack indoors and leave the bathroom door open after a shower. If the bedroom still reads under 40 percent overnight, a cool-mist humidifier closes the rest of the gap.
What are signs of too little humidity?
The everyday signs are a dry or sore throat on waking, a dry nose overnight that breaks up your sleep, static shocks off carpet and door handles, itchy or flaking skin, and eye irritation that contact lens wearers notice first. In winter it can also show up as the seasonal uptick in colds and flu-like illness. The catch is that none of these prove a number, because the same complaints have other causes. Put a hygrometer in the bedroom, read it across a few days and overnight, and if it sits under 40 percent you have your answer.
Is a bedroom humidity of 70% considered high?
A bedroom at 70 percent relative humidity is high by every consensus figure. EPA's guidance is to keep indoor humidity below 60 percent and ideally between 30 and 50 percent, and the band the body is actually tuned to is 40 to 50 percent. Above 60 percent the room supports mold growth, dust-mite habitat, and condensation on cold surfaces, and mold needs only 24 to 48 hours of sustained surface moisture to establish.
Sources cited on this page
Every number on this guide page traces to one of the 5 sources below: 3 peer-reviewed, 1 government or regulatory.
Peer-reviewed
- Wolkoff, 2018 (Int J Hyg Environ Health 221:374-382)
- Reiman et al., 2018 (PLOS ONE 13:e0204337)
- Sterling et al., 1985 (Energy and Buildings 6:259-270)
Government & regulatory
Institutional & standards
- ASHRAE Standard 55-2020, Thermal Environmental Conditions for Human Occupancy
More guides like this one
Curious what you are breathing at home?
Get your free Stasis Score from just your address